All strings sent from the JDBC driver to the server are converted automatically from native Java Unicode form to the client character encoding, including all queries sent via Statement.execute(), Statement.executeUpdate(), Statement.executeQuery() as well as all PreparedStatement and CallableStatement parameters with the exclusion of parameters set using setBytes(), setBinaryStream(), setAsciiStream(), setUnicodeStream() and setBlob() .

Prior to MySQL Server 4.1, Connector/J supported a single character encoding per connection, which could either be automatically detected from the server configuration, or could be configured by the user through the useUnicode and characterEncoding properties.

Starting with MySQL Server 4.1, Connector/J supports a single character encoding between client and server, and any number of character encodings for data returned by the server to the client in ResultSets.

The character encoding between client and server is automatically detected upon connection. The encoding used by the driver is specified on the server via the character_set system variable for server versions older than 4.1.0 and character_set_server for server versions 4.1.0 and newer. For more information, see Sección 10.3.1, “Conjunto de caracteres y colación del servidor”.

To override the automatically-detected encoding on the client side, use the characterEncoding property in the URL used to connect to the server.

When specifying character encodings on the client side, Java-style names should be used. The following table lists Java-style names for MySQL character sets:

MySQL to Java Encoding Name Translations. 

Warning.  Do not issue the query 'set names' with Connector/J, as the driver will not detect that the character set has changed, and will continue to use the character set detected during the initial connection setup.

To allow multiple character sets to be sent from the client, the UTF-8 encoding should be used, either by configuring utf8 as the default server character set, or by configuring the JDBC driver to use UTF-8 through the characterEncoding property.